implement TagsViewController
implement PhotoListViewController
implement PhotoDetailViewController
support landscape orientation
implement zooming
Capitalize tags showed in table view in TagsViewController
implement RecentPhotos model and RecentViewController
Remove duplicities from recent photos
show navigation bar titles in PhotoListViewController and PhotoDetailViewController
fix bug that causes duplicities in Recent Photos model
sort tags displayed in table on Tags screen and photo names displayed in table of photos for particular tag. (Extra Credit #1)